Causes of involutional ectropion and entropion--age-related tarsal changes are the key

To measure tarsal plates across various age-groups, to determine whether tarsal size changes with increasing age and whether size correlates with involutional ectropion and entropion.

Comparative, observational, case-control study design. Data were obtained for length and height of tarsus in each of the four eyelids. The data were constructed to determine: (I) right-to-left-side comparison data, (II) sex difference data, (III) age normal data, (IV) involutional entropion data, (V) involutional ectropion data.

(I) There is no difference in tarsal dimensions between right and left sides; (II) males have larger tarsal dimensions than females; (III) tarsal plates are on average smaller in older age ranges; (IV) patients with entropion have smaller than average age-normal tarsal plates; (V) patients with ectropion have larger than average age-normal tarsal plates.

(I) Right and left tarsal plates have equal dimensions, and involutional changes likely occur on both right and left sides equally frequently; (II) males have larger tarsal plates than females and entropion is more frequent in females and ectropion in males; (III) tarsal plates may have a general tendency to atrophy or shrink with age; this may explain why some eyelids develop entropion and others ectropion; (IV) entropion results from the mechanical effect of an atrophied or smaller than age-normal, partially or fully disinserted, tarsal plate being overcome by the normal or increased tone of the preseptal/pretarsal orbicularis muscle; (V) ectropion results from an age-normal or larger than normal tarsal plate mechanically overcoming the normal or decreased tone of the preseptal/pretarsal orbicularis muscle in combination with medial/lateral canthal tendon laxity.